• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.4
• /
• pp.1416-1425
• /
• 1996

A numerical method has been proposed to predict 3-dimensional flow in a duct system with multiple outlets. For the duct system, it is supposed that the pressure values are given at multiple outlets while the velocity profile is given at a inlet. To maintain the continuity of pressure distribution between main and branch duct, present method allows that the pressure value taken from analysis of branch duct can be converted to the main duct analysis. The result from present method which can handle the pressure boundary condition closely coincided with that from regular method which can handle the velocity boundary condition only. Furthermore the flow distribution from present method showed good agreement with that from the single block method. From the comparison of the present method with the total pressure method used for engineering duct design, 13% of discrepancy in pressure loss was shown between the main duct inlet and the branch duct outlet.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.8
• /
• pp.2611-2625
• /
• 1996

A numerical method on multi-block technique by Bi-CGSTAB(Bi-Conjugate Gradient STABilized) solver has been proposed. The present multi-block technique can reduce the numerical manipulation greatly because the common regions at the interface of each block are not necessary. In order to test the computational performance of present multi-block technique, the flow characteristics in a T type duct system and a N type duct system have been investigated by three kinds of methods such as the single-block method, the previous multi-block technique and the multi-block technique with Bi-CGSTAB solver. The results indicated that the required CPU time by present multi block technique was shorter than that of other two numerical methods and the convergency history was shown very stable at the present multi-block technique.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.946-948
• /
• 2002

최근 컴퓨팅 기술의 발전으로 3차원 복합열전달(conjugate heat transfer) 문제를 계산하는 수 치해석 기술이 어느 정도 가능해 졌지만, 실제적인 전력기기 내부의 온도분포를 수치적으로 계산하는 것은 탑재된 구성요소의 다양한 크기와 형상으로 인한 매우 복잡한 경계조건을 수반하고 조밀한 격자를 요구하기 때문에 공학적이지 않다. 이를 위하여 해석적 모델을 수립하여 전력기기 열설계를 위한 수치적 해석에 적용하는 방법이 널리 사용되고 있다. 본 연구에서는 열회로망법(Thermal Network Analysis, TNA)을 이용하여 전력기기 내부의 온도분포를 예측할 수 있는 프로그램을 개발하였다. 전류가 흘러 열이 발생하고 소산되는 주회로 성분들을 각각의 노드로 분할하는 절차를 확립하였고 열접촉저항과 주울열을 적절히 선정함으로써 실제 전류가 흐르는 회로망 내 온도분포를 계산하였다.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.48 no.4
• /
• pp.19-28
• /
• 2020

The Urban Heat Island (UHI) Effect has intensified due to urbanization and heat management at the urban level is treated as an important issue. Green space improvement projects and environmental policies are being implemented as a way to alleviate Urban Heat Islands. Several studies have been conducted to analyze the correlation between urban green areas and heat with linear regression models. However, linear regression models have limitations explaining the correlation between heat and the multitude of variables as heat is a result of a combination of non-linear factors. This study evaluated the Heat Island alleviating effects in Seoul during the summer by using a deep neural network model methodology, which has strengths in areas where it is difficult to analyze data with existing statistical analysis methods due to variable factors and a large amount of data. Wide-area data was acquired using Landsat 8. Seoul was divided into a grid (30m × 30m) and the heat island reduction variables were enter in each grid space to create a data structure that is needed for the construction of a deep neural network using ArcGIS 10.7 and Python3.7 with Keras. This deep neural network was used to analyze the correlation between land surface temperature and the variables. We confirmed that the deep neural network model has high explanatory accuracy. It was found that the cooling effect by NDVI was the greatest, and cooling effects due to the park size and green space proximity were also shown. Previous studies showed that the cooling effects related to park size was 2℃-3℃, and the proximity effect was found to lower the temperature 0.3℃-2.3℃. There is a possibility of overestimation of the results of previous studies. The results of this study can provide objective information for the justification and more effective formation of new urban green areas to alleviate the Urban Heat Island phenomenon in the future.

• Geophysics and Geophysical Exploration
• /
• v.12 no.1
• /
• pp.56-68
• /
• 2009

Ongoing and extensive urbanisation, which is frequently accompanied with careless construction works, may threaten important archaeological structures that are still buried in the urban areas. Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) methods are most promising alternatives for resolving buried archaeological structures in urban territories. In this work, three case studies are presented, each of which involves an integrated geophysical survey employing the surface three-dimensional (3D) ERT and GPR techniques, in order to archaeologically characterise the investigated areas. The test field sites are located at the historical centres of two of the most populated cities of the island of Crete, in Greece. The ERT and GPR data were collected along a dense network of parallel profiles. The subsurface resistivity structure was reconstructed by processing the apparent resistivity data with a 3D inversion algorithm. The GPR sections were processed with a systematic way, applying specific filters to the data in order to enhance their information content. Finally, horizontal depth slices representing the 3D variation of the physical properties were created. The GPR and ERT images significantly contributed in reconstructing the complex subsurface properties in these urban areas. Strong GPR reflections and highresistivity anomalies were correlated with possible archaeological structures. Subsequent excavations in specific places at both sites verified the geophysical results. The specific case studies demonstrated the applicability of ERT and GPR techniques during the design and construction stages of urban infrastructure works, indicating areas of archaeological significance and guiding archaeological excavations before construction work.